Systems for removing ozone



Aug. 30, 1966 .1. E. BoBERG ET AL SYSTEMS FOR REMOVING ozoNE originalFiled oct. zo, 1961 2 Sheets-Sheet 1 E41 liv N ...mi

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SYSTEMS FOR REMOVING OZONE Original Filed Oct. 20, 1961 2 Sheets-Sheet 2TEMPERATURE EFFEcT oN B FILTER MATERIALS usED IN ozoNE REMOVAL zo l,

TEMPERATURE F FIG 3 INVENTORS JOHN E. BOBERG MYRON LEVINE gent 9 cnims.(ci. as zss) This application is a divisional application of Serial No.146,525, led October 20, 1961, now abandoned.

This invention pertains to the removal of ozone from air.

The removal of ozone from air which is used for human consumption israpidly becoming a critical problem in the aircraft field. This isbecause passenger aircraft are presently being utilized and designedwhich are adapted to iy at extremely high altitudes. For economicreasons it is necessary to supply the passengers in such aircraft withambient air from around such aircraft rather than to supply them withair from a compressed source of this gas mixture.

In order to supply air to aircraft passengers it has been proposed toequip aircraft with a scoop type of air inlet which, during theoperation of the aircraft, gathers up air as the aircraft progresses,and compresses such air prior to its being conveyed from the inlet tothe distribution system used in the aircraft. The air obtained in thismanner is frequently referred to as ram air. As a consequence of suchcompression the air supplied to the interior of an aircraft is normallyheated to a material extent. With this type of system the air conveyedto the interior of an aircraft from an inlet as referred to above may beat a temperature of about 500-600 F.

Unfortunately at relatively high altitudes the air supplied to theinterior of an aircraft in the general manner referred to above is notsatisfactory for human consumption for several different reasons. One ofthese is, of course, the temperature of such air. Another very importantreason why such air cannot be consumed is the fact that it will normallycontain a significant proportion of ozone, the proportion of such ozonebeing related to the altitude at which such air is obtained, or in otherwords, the altitude at which the aircraft is flying.

This may be determined by referring to published information showing thedistribution of ozone at various altitudes. As an example of this, thecurve identified as FIGURE. l in Boberg and Levines Paper No. 6l-Av-2 ofthe American Society of Mechanical Engineers presented at the AviationConference of this organization at Los Angeles, California, March 12-15,1961, shows that a maximum of about 6 ppm. of ozone is found in theatmosphere in an elevation of about 85,000 ft. Ozone concentrations inexcess of l p.p.m. are normally considered to be lethal. Industrialhygienists have determined that the maximum safe or allowableconcentration of ozone in air for human consumption is about 0.1 ppm. Ingeneral it can safely be assumed that dangerous quantities of ozone willbe found in the atmosphere at elevations of from about 30,000 ft. toabout 150,000 ft.

An object of the present invention is to provide means for removingozone from the so-called ram air gathered up by an aircraft within thislatter altitude range. Another object of the present invention is toprovide means of this type which may be constructed at a comparativelynominal cost, which are easily utilized, and which are capable ofproviding prolonged, satisfactory service. A related object of thepresent invention is to provide new and improved catalysts for use withthese means for the purpose of causing decomposition of ozone intooxygen.

States Patent C) 3,259,81 Patented August 30, 1966 lCC Various otherobjects as well as many specific advantages of this invention will bemore fully apparent from a detailed consideration of the remainder ofthis specification including the accompanying drawings in which:

FIGURE 1 is a diagrammatic view of an apparatus adapted to be used in anaircraft capable of dying at an altitude in the range of from30,000-l50,000 ft. for use in removing the ozone from ambient airsupplied to the interior of such an aircraft;

FIGURE 2 is a diagrammatic view of a modified apparatus similar to theapparatus as set forth in the preceding figure; and

FIGURE 3 is a curve showing the operation of certain materials inremoving and decomposing ozone at various temperatures.

As an aid to understanding this invention it can be stated inessentially summary form that it concerns the removal of ozone from highaltitude air in an aircraft through the use of a catalytic bed, anadsorptive bed and a heat exchanger. Preferably the catalytic bed isconstructed so as to utilize solid strands or particles having surfacescapable of effectively decomposing ozone upon contact with this gas,these strands or particles being capable of withstanding the physicalstresses and strains encountered in an aircraft and resulting fromcontact with so-called ram air.

The Ireasons for the utilization with this invention of two differenttypes of beds for removal of ozone and of a heat exchanger will Ibeapparent from a consideration of FIGURE 3 of the accompanying drawings.In this figure the percentage of ozone capable of being removed from airby a bed of common adsorptive agent, activated charcoal, at varioustemperatures is designed as curve A While the percentage of ozonecapable of being removed from air lby decomposition at varioustemperatures by a nickel wool catalyst bed is plotted as curve B. Otheradsorptive and catalytic agents for the removal of ozone remove this gasfrom air in the same general manner indicated by these curves. Thus, thecorresponding curves for these other agents are nearly the same as thecurves shown. From FIGURE 3 it will -be seen that the effectiveness ofan adsorptive agent in removing ozone by adsorption decreases withtemperature while the effectiveness of the catalyst in decomposing ozoneincreases with temperature. Since the temperature of ram air in anaircraft will vary depending upon the manner of aircraft operation, thealtitude of Hight, the amount of compression of the ram air and otherfactors, it Will be apparent from a study of FIGURE 3 that no one typeof material is capable of effective ozone removal under all conditionsencountered in aircraft ights.

In accordance With this invention beds of two dierent types of materialsfor the removal of ozone may be used in series as indicated in theapparatus or system 10 shown in FIGURE 1 of the drawings. In theapparatus 10 air, `labeled ram air, from around an aircraft is picked upby an inlet scoop 12 and is compressed Iby the progress of the aircraftand is conveyed through a short conduit 14 to a canister 16 containing acatalytic bed (not separately shown). From this canister 16 it isconveyed to a heat exchanger 18 through another conduit 20. In the heatexchanger 18 the air from the canister 16 may Ibe mixed wit-h are-cycled cabin air (air used in an aircraft) conveyed from anotherconduit 22, and is cooled through the use of a conventional coolant (notillu-strated) supplied to and removed from the hea-t exchanger 18through conduits 24. From the heat exchanger 18 the air cooled in it ispassed through another conduit 28 to a canister 30 containing a 'bed ofadsorptive material (not separately shown), and from this canister 30 itis passed into the interior of an aircraft through a further conduit E34. The canisters 16 and 30 and the heat exchanger 18 can be constructedin a number of different known manners; because of Athis theirconstructions are not set forth in this specification.

As an aircraft containing the apparatus is operated Iram air will bepicked up by the scoop 12, and, by virtue of the movement of theaircraft will be compressed as it is picked up. Such compression willcause the ram air to become heated. The ram air passing into thecanister 16 will come in contact with the catalytic agent within thiscanister 16 so as to decompose a percentage of ozone, which percentageis dependent upon .the temperature of the ram air. In general, thistemperature will be primarily dependent upon the speed of the aircraft.Hence, the faster the flight of the aircraft, in general, the greaterthe proportion of ozone in the ram air converted or decomposed tooxygen, O2, in the canister 16. The temperature of the air leaving thiscanister 16 during the use of the apparatus 10 is lowered to atemperature at which practically all of the residual ozone remaining init is capable of being adsorbed by the material in the canister 30 bythe heat exchanger 18. Thus, with the apparat'us 10, the air supplied tothe interior of an aircraft through the conduit 34 will be substantiallyozone free as a consequence of two different mechanisms of ozone removalwhich are effective at different temperatures.

Obviously Ithe apparatus 18 will not always operate so that the twodiiferent beds of materials in the canisters 16 and 30 remove ozoneprecisely as indicated in the curves A and B in FIGURE 3 since theoperation of these beds of materials will be dependent upon a number offactors such as, for example, the materials within these beds, thethicknesses of these beds of materials, the surface areas available forcontact with ram air in these beds, the resistance to the flow of ramair exercised by these |beds of materials and the like. The operation ofthe entire apparatus 10 should be carried under such conditions that anappropriate allowance is made for any heating effect which may beencountered by ram air passing through the various parts of thisapparatus.

In general, the heat exchanger 18 should be operated so that the airconveyed through the canister 30 is cooled to a temperature at which inexcess of about 90% of the ozone passing through the canister isadsorbed by the material in it. This temperature may be considered asless than about 300 F. as can be seen from an examination of curve A inFIGURE 3. In order to increase the efficiency of t'he operation of thecatalytic material within the canister 16 preferably the entireapparatus 10 is operated s0 that the ram air supplied to this canister16 is as hot as reasonably possible. In general the ram air supplied tothe canister 16 should be at a temperature in excess of about 300 F. .inlorder to accomplish as much removal or decomposition of ozone asreasonably possible in this canister 16.

A number of different materials may be used as catalysts for thedecomposition of ozone within the canister 16 in the apparatus 10.Particularly favorable results in removing ozone from air at 600 F. havebeen achieved by utilizing fine strands of nickel wool 38 packed withina canister such as the canister 16. Other less effective catalyticmaterials in order of decreasing effectiveness when used in a like form-under the same conditions are gold, brass, aluminum and silver. Othercatalysts for the decomposition of ozone such as stainless steel,platinum, iridite aluminum and chromium are not as effective as theseinitially enumerated catalytic materials.

The form with which the catalytic material used in a canister such asthe canister 16 is employed may be varied within comparatively Widelimits. Thus, for example, metal catalysts utilized with this inventioncan be employed in the form of Wire strands woven into screens or likestructures which in turn may be located in virtually any desired type ofmanner so as to achieve an air ow through them. Similarly various metalsused as catalysts with the present invention can be located by plating,vapor phase deposition or the like upon various inert or other supportssuch as nely divided glass fibers or the like. Similarly, pellets orparticles of various metals, as indicated in the preceding, can beemployed as catalysts, or pellets or particles of inert materials coatedwith catalytic agents as herein described may be utilized. Ifnon-metallic catalysts, such as manganese dioxide are to be used in anapparatus such as the apparatus 10 to decompose ozone, pellets of suchnonmetallic materials may be located within the canister 16.

With the present invention it is normally preferred to utilize metallicstrands of catalytic material in the canister 16 since such strandspossess a relatively high amount of physical strength, are capable ofwithstanding the vibration encountered during the operation of anaircraft and are capable of withstanding the pressure of ram air appliedto them in a canister such as the canister 16 without coming apart ordecomposing in a physical sense. Thus, When strands of metal are used ascatalysts in the canister 16 there is substantially no chance of thecatalytic material passing from this canister 16 into the various partsof the apparatus 10.

In general, the purer the catalytic materials employed, the moreefficient the ozone decomposition achieved as a consequence of theiruse. Further, in general, the greater the time of contact of a givenamount of ram air wvithin these materials, the greater the decompositionof ozone. Since ozone is relatively unstable at elevated temperaturesthe greater the duration of the time ram air containing ozone is heldwithin various parts of the complete apparatus 10, and in particularwith the conduits 14 and 2t) and the canister 16, the greater the amountof ozone which will be decomposed without any catalytic eifect causingsuch decomposition.

Time alone will, for the same reasons, cause a partial reduction in theamount of ozone passing through the canister 30 containing adsorptivematerial in the apparatus 10. Presently preferred results have beenachieved by using -as this adsorptive material particles of commonactivated charcoal, although other common known adsorbents may besubstituted for this particular adsorbent. Similarly it is preferred toalways utilize an adsorbent material such as activated charcoal which iscapable of being rejuvenated in accordance with known techniques afterit has become contaminated with ozone. It is considered possible thatany adsorbent material used may exercise some catalytic effect inpromoting the decomposition of ozone as well as an adsorbent effect.Obviously whatever adsorbent material is used in the canister 30 in theapparatus 10 it 1will periodically have to be replaced or rejuvenatedsince its effectiveness as an adsorbent for ozone will decreasedepending upon the amount of ozone adsorbed by it.

In FIGURE 2 of the drawing there is shown a modied system or apparatus50 for use in removing ozone from atmospheric air utilized in anaircraft which is closely related to the apparatus 10 previouslydescribed. In the apparatus 50 atmospheric air labelled in the drawingas ram air is picked up by an inlet scoop 52 as the aircraft isoperated. This scoop 52 holds such air so that it is compressed andraised in temperature during flight. From the scoop 52 this ram air isconveyed through a short conduit 54 to a valve 56 having a movable valvebody 58 which is capable of being actuated so as to direct the ram airinto either a conduit 60 or a conduit 62.

When the ram air is passed through the conduit 60 it is directed into acanister 64 corresponding to the canister 30 previously described. Thiscanister 64 may be filled with an adsorptive material as indicated inthe preceding discussion. When the ram air is directed into the conduit62 it passes into a canister 68 corresponding to the canister 16previously described where it passes in engagement with the surface of acatalytic material of the type indicated in the preceding discussionwhich is capable of decomposing ozone by contact with this gas.

The outlets from the canisters 64 and 68 are connected together by meansof further conduits 70 which lead to a heat exchanger 72 correspondingto the heat exchanger 18 previously described. In this heat exchanger 72the ram air may be mixed with recirculated cabin air conveyed to theexchanger 72 through a conduit 74 before it is supplied to the interiorof an aircraft at a useful temperature, capable of being tolerated by ahuman being, through a further conduit 76. Conduits 78 are used tosupply to and remove from the heat exchanger 72 a coolant fluid (notseparately shown).

From a consideration of the apparatus 50 it will be realized that thecanisters 64 and 68 are connected in parallel, whereas in the apparatusthe canisters 16 and 30 are connected in series with one another. Withthe apparatus 50 the valve 56 is normally operated so as to direct ramair at temperatures of less than about 300 F. through the canister 64and so as to direct ram air at greater temperatures than this throughthe canister 68. With this mode of operation the materials within thecanisters 64 and 68 are used within the temperature ranges in which theymost effectively remove ozone.

This specifica-tion is based upon invention subject matter set forth inthe Boberg and Levine Paper Number 6l- Av-2 of the American Society ofMechanical Engineers referred to earlier in this specification. For thepurposes of brevity material set forth in this paper which is notconsidered necessary for an understanding of the present invention hasbeen omitted from this specification. However, the entire contents ofthis Paper 6l-Av-2 are incorporated herein by reference for the purposeof amplifying the disclosure of this specification.

It is to be understood that the foregoing description is by way ofillustration, and that changes, omissions, additions, substitutions and/0r modications may be made within the scope of the claims withoutdeparting from the spirit of the invention.

What is claimed is:

1. An apparatus for removing ozone from air entering an aircraft cabincomprising: means for admitting ram air; means for catalyticallydecomposing the ozone in said air connected to 4the ram air admittingmeans; heat exchanger means for cooling air connected to said means forcatalytically decomposing ozone so as to receive air from said means forcatalytically decomposing ozone; means for ducting recycled cabin ai1into the heat exchanger means; and means for adsorbing ozone from airconnected to said heat exchanger means so as to receive air from saidheat exchanger means.

2. An apparatus as defined in claim 1 wherein said means forcatalytically decomposing ozone comprises:

canister means, and metal strands having surfaces capable of decomposingozone located within said canister means.

3. An apparatus as defined in claim 2 wherein said metal strands arenickel strands.

4. An apparatus as defined in claim 1 wherein said means for adsorbingozone comprises: canister means and activated charcoal particles locatedwithin said canister means.v

5. An apparatus for removing ozone from atmospheric air entering anaircraft cabin comprising: a ram air inlet means for obtaining air fromthe atmosphere; valve means connected to said air inlet means so as toreceive air from said air inlet means; means for catalyticallydecomposing ozone connected to said valve means; means for adsorbingozone in air connected to said valve means, said valve means directingair into either said means for catalytically decomposing ozone or saidmeans for adsorbing ozone; and a heat exchanger being coupled to theozone decomposing means and ozone adsorbing means.

6. An apparatus as defined in claim 5 wherein said means forcatalytically decomposing ozone comprises: canister means, and metalstrands having surfaces capable of decomposing ozone located within saidcanister means.

7. An apparatus as dened in claim 6 wherein said metal strands arenickel strands.

S. An apparatus as defined in claim 5 wherein said means for adsorbingozone comprises: canister means and activated charcoal particles locatedwithin said canister means.

9. An apparatus as defined in claim 5 wherein said means for decomposingozone comprises: canister means, and manganese dioxide pellets locatedwithin said canister means.

References Cited by the Examiner UNITED STATES PATENTS 1,961,878 6/1934Giikey 23-4 2,872,397 2/1959 Kirrer 23-281 x 2,980,494 4/1961 Jenkins eta1. 23-4 3,151,943 10/1964 Fujimoto et a1. 23-222 X OTHER REFERENCESRideal, Ozone, page (1920), Constable and Co. Ltd., London.

MORRIS O. WOLK, Primary Examiner.

0 JOSEPH scovRoNEK, Examiner.

1. AN APPARATUS FOR REMOVING OZONE FROM AIR ENTERING AN AIRCRAFT CABINCOMPRISING: MEANS FOR ADMITTING RAM AIR; MEANS FOR CATALYTICALLYDECOMPOSING THE OZONE IN SAID AIR CONNECTED TO THE RAM AIR ADMITTINGMEANS; HEAT EXCHANGER MEANS FOR COOLING AIR CONNECTED TO SAID MEANS FORCATALYTICALLY DECOMPOSING OZONE SO AS TO RECEIVE AIR FROM SAID MEANS FORCATALYTICALLY DECOMPOSING